Since Si-containing materials (porous or dense) containing Si as a Si phase such as, for example, silicon-silicon carbide composite materials containing Si and SiC as main phases or materials containing silicon carbide as a main phase have a high strength and moreover are superior in heat resistance, oxidation resistance and heat conductivity, they are currently in use in various applications such as kiln tool, jig for heat treatment, honeycomb filter and the like.
At the time of the above-mentioned Si-containing material, there has been mainly used a kiln tool made of a dense SiC material to which BN, B4C and C have been added in an amount of 1% as a superaddition, or of a carbon having been coated with BN as a reaction-preventive layer.
However, Si-containing materials produced using the above kiln tool have had a problem that the actual heat conductivity is far smaller than the designed heat conductivity.
The present invention has been made in view of the above-mentioned problem of the prior art and aims at providing a highly heat-conductive Si-containing material in which, by controlling the lattice constant of the Si phase at room temperature, a reduction in heat conductivity can be prevented and a high heat conductivity can be exhibited stably, and a process for producing such a Si-containing material.